1. Field of the Invention
This invention generally relates to an input device such as a touch panel, switch, or the like. The touch panel is used for detecting coordinates of a position pushed by, for example, a pen, a finger, or the like, and the input device is used for detecting a position inputted by a finger or the like.
2. Description of the Related Art
Conventionally, panel-shaped input devices named touch panel input device and touch pad input device have been proposed. The touch panel input device includes a display overlapping a touch sensor. The touch pad is used with a personal computer. Information to the above-mentioned panel-shaped input devices is generated by touching a position that corresponds to, for example, buttons displayed on a screen with an attached pen or by touching inside an operation range at certain intervals.
In the case where the above-mentioned panel-shaped input devices, are used as an input switch, a plane switch such as a touch panel does not give a feeling of click as if a mechanical switch were pushed down. This is a drawback in that a user cannot recognize a pushdown.
Japanese Patent Application Publication No. 2003-122507 (hereinafter referred to as Document 1) discloses a touch panel input device in order to solve the aforementioned drawback. FIG. 1 is a perspective view of a conventional touch panel input device. Referring to FIG. 1, a touch panel input device 1 includes a piezoelectric substrate 2. The piezoelectric substrate 2 is arranged between an upper movable plate 3 and a lower supporting substrate 4. The piezoelectric substrate 2 is conducted, when a movable conductive material layer 6 touches a fixed conductive material layer 7 according to an input from a touch panel. The piezoelectric substrate 2 expands and contracts to apply vibrations to the movable plate 3. Japanese Patent Application Publication No. 6-7408 (hereinafter referred to as Document 2) discloses a device that gives a sense of touch. FIG. 2 is a cross-sectional view of the device that gives the sense of touch. Referring to FIG. 2, the device 10, which gives the sense of touch, includes a protruded surface 11, a vibration plate 12, a movable coil 13, a connecting chassis 14, and a magnet 15. The vibration plate 12 is vibrated by an electromagnetic force generated between the movable coil 13 and the magnet 15. The sense of touch is given to a finger, when the finger touches the protruded surface 11.
The touch panel input device disclosed in Document 1, however, the upper movable plate 3 and the lower supporting substrate 4 are normally configured to integrate due to a bonded structure, although the piezoelectric substrate 2 is arranged between the upper movable plate 3 and the lower supporting substrate 4 so as to vibrate the upper movable plate 3. This bonding structure makes it impossible to provide a sufficient gap between the upper movable plate 3 and the lower supporting substrate 4. That is to say, the upper movable plate 3 cannot retain a sufficient amount of mechanical displacement. This makes it impossible to give the feeling of click, when the panel is pushed down.
The device giving the sense of touch disclosed in Document 2 includes the protruded surface 11 on a top face of the vibration plate 12. There is a problem in that the device disclosed in Document 2 cannot be used as the input device, because it is hard to recognize a display device or electric decoration, if the display device or electric decoration is provided on a backside of the protruded surface 11.